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SX-Key ok, Without Not — Parallax Forums

SX-Key ok, Without Not

John CoutureJohn Couture Posts: 370
edited 2007-09-26 07:09 in General Discussion
Short of having to tear the board apart, does anyone have any words of wisdom?

SX chip blinks LED's ok when SX-Key is attached, but LED's don't blink when I disconnect the Key.

a) possible bad Resonator?

other ideas?

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John J. Couture

San Diego Miramar College

Comments

  • John CoutureJohn Couture Posts: 370
    edited 2007-09-24 00:34
    Ok, followup.

    I put a 1meg resistor across the osc1 and osc2 pins and it started working. In Gunther Daubach book it shows a resistor (R2) on page 6 and the caption says "Depends on the resonator, or crystal type"

    I'm using a two pin resonator (it does not have a middle ground pin).

    Can anyone shed any light on WHY it works?

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    John J. Couture

    San Diego Miramar College
  • BeanBean Posts: 8,129
    edited 2007-09-24 11:53
    The resonator (or xtal) needs to have capacitors on either side to ground.
    The three pin resonators have these caps built-in.

    What frequency resonator are you using ? and what OSC settings are you using on the DEVICE line ?

    Bean.

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  • John CoutureJohn Couture Posts: 370
    edited 2007-09-25 22:50
    Thank you Bean.

    Didn't work so I must be doing something stupid.· The resistor worked some of the time and when I put my hand next to the osc1/2 connector it seemed to blink again.· So it must have something to do with capacitance.

    As per your suggestion I connected a 223 cap (.022 uf?) from osc1 to ground and another one from osc2 to ground but that didn't work.

    It's just a simple program with

    DEVICE········· SX18, OSCXT2, TURBO, STACKX, OPTIONX
    FREQ··········· 4_000_000
    ID············· "E622-01"

    I seem to remember you saying once that breadboards have a lot of capacitance.·

    This project is built on a perfboard and I built a second one to see if I was messing up something.· I guess it's time to start on the third one and see if I should change the design.

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    John J. Couture

    San Diego Miramar College
    SXB
    SXB
    exp622-01b.SXB
    3K
    pdf
    pdf
    scan00158.pdf
    238K
  • StarManStarMan Posts: 306
    edited 2007-09-26 07:09
    I had a similar problem recently.· http://forums.parallax.com/showthread.php?p=670135

    I am using the 3-lead resonators on a SX28 Proto board.· Never did figure it out.· I'll try the resistor trick.

    Chris

    ·
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